Aline C. C. Rotzetter

Thermoresponsive Polymer Induced Sweating Surfaces as an Efficient Way to Passively Cool Buildings

Buildings can be effectively cooled by a bioinspired sweating-like action based on thermoresponsive hydrogels (PNIPAM), which press out their stored water when exceeding the lower critical solution temperature. The surface temperature is reduced by 15 °C compared to that of a conventional hydrogel (pHEMA) and by 25 °C compared to the bare ground.

Dissolution and transformation of cerium oxide nanoparticles in plant growth media

From environmental modeling of engineered nanomaterial (ENM) release, it is clear that ENMs will enter soils, where they interact with soil compounds as well as plant roots. We analyzed three different size groups of cerium dioxide nanoparticles (CeO2-NPs) in respect to chemical changes in the most common plant growth medium, Hoagland solution. We created a simple environmental model using liquid dispersions of 9-, 23-, and 64-nm-uncoated CeO2-NPs. We found that CeO2-NPs release dissolved Ce when the pH of the medium is below 4.6 and in the presence of strong chelating agents even at pH of 8. In addition, we found that in reaction with Fe2+-ions, equimolar amounts of Ce were released from NPs. We could elucidate the involvement of the CeO2-NPs surface redox cycle between Ce3+ and Ce4+ to explain particle transformation. The chemical transformation of CeO2-NPs was summarized in four probable reactions: dissolution, surface reduction, complexation, and precipitation on the NP surface. The results show that CeO2-NPs are clearly not insoluble as often stated but can release significant amounts of Ce depending on the composition of the surrounding medium.

Combining Phosphate and Bacteria Removal on Chemically Active Filter Membranes Allows Prolonged Storage of Drinking Water

A chemically active filtration membrane with incorporated lanthanum oxide nanoparticles enables the removal of bacteria and phosphate at the same time and thus provides a simple device for preparation of drinking water and subsequent safe storage without using any kind of disinfectants.

Sintering of core–shell Ag/glass nanoparticles: metal percolation at the glass transition temperature yields metal/glass/ceramic composites

In order to investigate the sintering evolution of core/shell metal/glass nanoparticles, two model compounds were synthesized and their structural evolution was investigated. Silica glass coated Ag nanoparticles were synthesized by flame spray pyrolysis, pressed into bulk pills and subsequently sintered at different temperatures finally resulting in composites with a highly conductive percolated silver network embedded in a ceramic matrix. By synthesizing two glass silver nanocomposites differing in their glass composition and corresponding glass transition temperature, the direct influence of the glass matrix on the percolation network formation and the conductive properties could be investigated. The analysis of the two systems by X-ray diffraction, scanning and transmission electron microscopy and by energy-dispersive X-ray detection clearly showed that the formation of the percolated network is initiated at the glass transition temperature of the matrix.

Rapid surface-biostructure interaction analysis using strong metal-based nanomagnets

Nanomaterials are increasingly suggested for the selective adsorption and extraction of complex compounds in biomedicine. Binding of the latter requires specific surface modifications of the nanostructures. However, even complicated macromolecules such as proteins can afford affinities toward basic surface characteristics such as hydrophobicity, topology, and electrostatic charge. In this study, we address these more basic physical interactions. In a model system, the interaction of bovine serum albumin and amyloid β 42 fibrillar aggregates with carbon-coated cobalt nanoparticles, functionalized with various polymers differing in character, was studied. The possibility of rapid magnetic separation upon binding to the surface represents a valuable tool for studying surface interactions and selectivities. We find that the surface interaction of Aβ 42 fibrillar aggregates is mostly hydrophobic in nature. Because bovine serum albumin (BSA) is conformationally adaptive, it is known to bind surfaces with widely differing properties (charge, topology, and hydrophobicity). However, the rate of tight binding (no desorption upon washing) can vary largely depending on the extent of necessary conformational changes for a specific surface. We found that BSA can only bind slowly to polyethylenimine-coated nanomagnets. Under competitive conditions (high excess BSA compared to that for β 42 fibrillar aggregates), this effect is beneficial for targeting the fibrillar species. These findings highlight the possibility of selective extractions from complex media when advantageous basic physical surface properties are chosen.